It is known that anthra[2,1-c][1,2,5]thiadiazole-6,11-dione (Formula I), a kind of anthraquinone derivative containing a heterocyclic group, is a cyclic compound produced by the reaction of 1,2-diaminoanthraquinone and thionyl chloride via catalyzation by triethylamine. It is disclosed in Taiwan Patent application number 097112087 that the compound was evaluated in the full panel of human tumor cell lines derived from different cancer cell types such as leukemia, non-small cell lung cancer, colon cancer, etc. at the National Cancer Institute (NCI) and shows anti-proliferative activity against human cancer cell lines.

The known tricyclic anthraquinone derivatives, for example, the 2,3-dihydroimidazo[1,2-c]quinazoline compounds disclosed in Taiwan Patent No. 1378792; Taiwan Patent No. 1402066; Taiwan Publication No. 201249792 and Taiwan Publication No. 200840582 can be used for the treatment of the excessive growth of cancer cells and the formation of the vessels accompanying the cells. In addition to the effects mentioned above, the compounds disclosed in Taiwan Patent No. 1245036 not only inhibit tumor cell lines, but also have anti-allergic and anti-inflammatory properties as well. However, existing literature does not disclose whether anthraquinone derivatives can ease pain or can be applied to pharmaceutical use as an analgesic.
In order to overcome the drawbacks in the prior art, an indication of anthra[2,1,c][1,2,5]thiadiazole-6,11-dione compound for alleviating pain is disclosed. The particular design in the present invention not only solves the problems described above, but is also easy to implement. Thus, the present invention has substantial utility for the industry.